package handlers

import (
	"context"
	"errors"
	"log/slog"
	"os/exec"
	"strconv"
	"strings"

	"github.com/gin-gonic/gin"

	"git.netcell-it.de/projekte/edgeguard-native/internal/handlers/response"
	"git.netcell-it.de/projekte/edgeguard-native/internal/models"
	"git.netcell-it.de/projekte/edgeguard-native/internal/services/audit"
	"git.netcell-it.de/projekte/edgeguard-native/internal/services/forwardproxy"
)

type ForwardProxyHandler struct {
	Repo     *forwardproxy.Repo
	Audit    *audit.Repo
	NodeID   string
	Reloader func(ctx context.Context) error
}

func NewForwardProxyHandler(repo *forwardproxy.Repo, a *audit.Repo, nodeID string, reloader func(context.Context) error) *ForwardProxyHandler {
	return &ForwardProxyHandler{Repo: repo, Audit: a, NodeID: nodeID, Reloader: reloader}
}

func (h *ForwardProxyHandler) reload(ctx context.Context, op string) {
	if h.Reloader == nil {
		return
	}
	if err := h.Reloader(ctx); err != nil {
		slog.Warn("squid: reload after mutation failed", "op", op, "error", err)
	}
}

func (h *ForwardProxyHandler) Register(rg *gin.RouterGroup) {
	base := rg.Group("/forward-proxy")
	base.GET("/stats", h.Stats)

	g := base.Group("/acls")
	g.GET("", h.List)
	g.POST("", h.Create)
	g.GET("/:id", h.Get)
	g.PUT("/:id", h.Update)
	g.DELETE("/:id", h.Delete)
}

func (h *ForwardProxyHandler) List(c *gin.Context) {
	out, err := h.Repo.List(c.Request.Context())
	if err != nil {
		response.Internal(c, err)
		return
	}
	response.OK(c, gin.H{"acls": out})
}

func (h *ForwardProxyHandler) Get(c *gin.Context) {
	id, ok := parseID(c)
	if !ok {
		return
	}
	x, err := h.Repo.Get(c.Request.Context(), id)
	if err != nil {
		if errors.Is(err, forwardproxy.ErrNotFound) {
			response.NotFound(c, err)
			return
		}
		response.Internal(c, err)
		return
	}
	response.OK(c, x)
}

func (h *ForwardProxyHandler) Create(c *gin.Context) {
	var req models.ForwardProxyACL
	if err := c.ShouldBindJSON(&req); err != nil {
		response.BadRequest(c, err)
		return
	}
	if err := validateACL(&req); err != nil {
		response.BadRequest(c, err)
		return
	}
	out, err := h.Repo.Create(c.Request.Context(), req)
	if err != nil {
		response.Internal(c, err)
		return
	}
	_ = h.Audit.Log(c.Request.Context(), actorOf(c), "forward_proxy.acl.create", out.Name, out, h.NodeID)
	response.Created(c, out)
	h.reload(c.Request.Context(), "create")
}

func (h *ForwardProxyHandler) Update(c *gin.Context) {
	id, ok := parseID(c)
	if !ok {
		return
	}
	var req models.ForwardProxyACL
	if err := c.ShouldBindJSON(&req); err != nil {
		response.BadRequest(c, err)
		return
	}
	if err := validateACL(&req); err != nil {
		response.BadRequest(c, err)
		return
	}
	out, err := h.Repo.Update(c.Request.Context(), id, req)
	if err != nil {
		if errors.Is(err, forwardproxy.ErrNotFound) {
			response.NotFound(c, err)
			return
		}
		response.Internal(c, err)
		return
	}
	_ = h.Audit.Log(c.Request.Context(), actorOf(c), "forward_proxy.acl.update", out.Name, out, h.NodeID)
	response.OK(c, out)
	h.reload(c.Request.Context(), "update")
}

func (h *ForwardProxyHandler) Delete(c *gin.Context) {
	id, ok := parseID(c)
	if !ok {
		return
	}
	if err := h.Repo.Delete(c.Request.Context(), id); err != nil {
		if errors.Is(err, forwardproxy.ErrNotFound) {
			response.NotFound(c, err)
			return
		}
		response.Internal(c, err)
		return
	}
	_ = h.Audit.Log(c.Request.Context(), actorOf(c), "forward_proxy.acl.delete", strconv.FormatInt(id, 10), gin.H{"id": id}, h.NodeID)
	response.NoContent(c)
	h.reload(c.Request.Context(), "delete")
}

// Stats liefert Squid-Cache-Statistiken via `squidclient mgr:counters`.
// Die Ausgabe enthält HTTP-Header gefolgt von key = value Zeilen.
func (h *ForwardProxyHandler) Stats(c *gin.Context) {
	out, err := exec.Command("squidclient", "-h", "127.0.0.1", "-p", "3128", "mgr:counters").Output()
	if err != nil {
		response.OK(c, gin.H{
			"error": "squidclient nicht verfügbar: " + err.Error(),
		})
		return
	}
	response.OK(c, gin.H{"stats": parseSquidCounters(string(out))})
}

type squidStats struct {
	ClientRequests int64   `json:"client_requests"`
	CacheHits      int64   `json:"cache_hits"`
	CacheHitPct    float64 `json:"cache_hit_pct"`
	ClientErrors   int64   `json:"client_errors"`
	BytesIn        int64   `json:"bytes_in"`
	BytesOut       int64   `json:"bytes_out"`
	ServerRequests int64   `json:"server_requests"`
	ServerErrors   int64   `json:"server_errors"`
}

func parseSquidCounters(out string) squidStats {
	// squidclient prefixes an HTTP response header block — skip it.
	body := out
	if idx := strings.Index(out, "\r\n\r\n"); idx >= 0 {
		body = out[idx+4:]
	} else if idx := strings.Index(out, "\n\n"); idx >= 0 {
		body = out[idx+2:]
	}
	s := squidStats{}
	for _, line := range strings.Split(body, "\n") {
		k, v, ok := strings.Cut(line, "=")
		if !ok {
			continue
		}
		n, _ := strconv.ParseInt(strings.TrimSpace(v), 10, 64)
		switch strings.TrimSpace(k) {
		case "client_http.requests":
			s.ClientRequests = n
		case "client_http.hits":
			s.CacheHits = n
		case "client_http.errors":
			s.ClientErrors = n
		case "client_http.kbytes_in":
			s.BytesIn = n * 1024
		case "client_http.kbytes_out":
			s.BytesOut = n * 1024
		case "server.all.requests":
			s.ServerRequests = n
		case "server.all.errors":
			s.ServerErrors = n
		}
	}
	if s.ClientRequests > 0 {
		s.CacheHitPct = float64(s.CacheHits) / float64(s.ClientRequests) * 100
	}
	return s
}

// validateACL prüft Name (squid-konform), action, acl_type. Squid
// nimmt viele Typen — wir whitelisten die, die in einem Forward-
// Proxy-Setup üblich sind, damit Tippfehler nicht beim reload
// crashen.
func validateACL(a *models.ForwardProxyACL) error {
	if a.Name == "" {
		return errors.New("name required")
	}
	switch a.Action {
	case "allow", "deny":
	default:
		return errors.New("action must be allow or deny")
	}
	switch a.ACLType {
	case "src", "dst", "dstdomain", "srcdomain", "port",
		"proto", "method", "time", "url_regex", "urlpath_regex",
		"dstdom_regex", "srcdom_regex", "browser":
	default:
		return errors.New("acl_type not supported (allowed: src, dst, dstdomain, srcdomain, port, proto, method, time, url_regex, urlpath_regex, dstdom_regex, srcdom_regex, browser)")
	}
	if a.Value == "" {
		return errors.New("value required")
	}
	return nil
}